This invention relates to the modification or conversion of passenger carrying aircraft to freight carrying aircraft and, more particularly, to a method of supporting such an aircraft without damage while major structural components, particularly floor-beams, are being removed and replaced.
When aircraft are converted for freight carriage, stronger structural components are sometimes required as a result of the extra weight imposed by the cargo. This is accomplished by reinforcing some structural components and removing some of the weaker components and replacing them with stronger components. The quantity of structural components that may be removed concurrently is limited to prevent significant deformation of the aircraft. The greater the amount of work that may be accomplished concurrently, the quicker the aircraft may be put back into revenue generating service. The aircraft is supported, usually with jacks and cradles, in an attempt to minimize deformation.
The floor structure, which may consist of floor-beams, floor panels, seat tracks, intercostals, hard point fittings, cargo handling equipment, and hydraulic and electrical standoffs, often represents a significant quantity of the structural items that must be removed and replaced with stronger components. Replacement is usually limited to every other floor-beam at a time. This requires that each floor-beam be carefully located to ensure a flat level floor. The remaining floor structure is then located and installed. This installation is accomplished by mechanics working in confined quarters beneath the floor-beams or lying on top of the floor-beams. This difficult process is labor intensive and contributes significantly to the down time required to modify the aircraft. Small errors in locating parts often compound and result in re-assembly fit problems requiring unique repairs for each occurrence. This decreases the quality of the product and adds to the down time and the expense associated with the aircraft modification. Minor movement of the fuselage can also compound into re-assembly fit problems.
In the time period after the floor beams are installed and prior to the installation of the rest of the floor structure, the floor beams are unstable thus presenting hazardous conditions to individuals working inside the aircraft. In addition, dropped tools and parts represent a hazard to mechanics and other people working below the floor beams. Drill shavings, created while installing floor structure components, fall into the lower lobes of the aircraft. Cleaning up these drill shavings, in the confined area of the lower lobes is difficult and time consuming.